To charge the batteries of battery-fed devices, such as cellular phones, PDAs, remote controls, notebooks etc., or directly power devices such as lamps or kitchen appliances, an inductive power system enabling a wireless power transfer can be applied. Inductive power systems for transferring power or charging mobile devices are generally known. Such a system comprises a power transmitting device, hereafter called transmitter module, comprising one or more transmitter coils which can individually be energized, thereby generating an alternating magnetic field. The inductive power system is used for transferring power to a power receiving device, hereafter called receiver, which are connectable to, or part of, a device that is to be charged or provided with power. In order to receive the power, the power receiving device is provided with a receiver coil, in which the alternating magnetic field, provided by the energized transmitter coils, induces a current. This current can drive a load or, for example, charge a battery, power a display or light a lamp.
Document U.S. Pat. No. 7,576,514 describes a planar inductive battery charging system designed to enable electronic devices to be recharged. The system includes a planar power surface on which a device to be recharged is placed. Within the power surface is at least one and preferably an array of transmitter coils that couple energy inductively to a receiver coil formed in the device to be recharged. Various arrangements of transmitter coils are described to provide an uninterrupted power surface having a substantially constant density of transmitter coils. The application of such an array may be a general power surface for powering wireless devices, e.g. for charging batteries, integrated in furniture, or as floor or wall covering.